The present invention relates to a new and improved construction of apparatus for destacking a stack of flexible flat structures, especially unfolded or folded sheets or printed products, comprising a stack support in the form of revolvingly driven rolls, contact rails arranged above the stack support for defining a stack support surface, a separation device arranged below the stack support and revolvingly driven in rhythm with the arriving rolls for the continuous downward removal of the edge of the momentarily lowermost located flat structure between the arriving rolls, and a conveyor device engaging below the stack support for removing the printed products arriving beneath the stack support.
According to a prior art apparatus as disclosed in German patent publication No. 1,536,489 of comparable construction, there are provided removal or withdrawal rolls in a revolving roller frame between groups of support rolls forming the stack support. The withdrawal rolls are driven to rotate opposite to the direction of revolving motion of the roller frame. Furthermore, these withdrawal rolls have mounted thereat suction cups which engage at the pre-fold of the lowermost situated sheet of the stack which is to be destacked and transport such engaged sheet, following winding-up thereof onto the roll sheell or jacket during the course of the revolving motion of the roller frame, to a removal station, where the sheet must be unwound from the withdrawal roll, in order to thereafter be delivered to a separation device. With the aid of the revolvingly driven roll of the stack support it is intended to render possible, with this prior art apparatus, that the withdrawal rolls wind-off at the stack support surface and thus are capable of winding-up the lowermost sheet.
Furthermore, an apparatus of the previously mentioned type is known form German patent publication No. 2,260,789. Here, the stack support is formed by a series of rolls or rollers which are anchored at their ends in bearing rings and thus are grouped together into a rotatably driven drum. In similar fashion, yet with fewer rolls, the separation device likewise forms a drum which is eccentrically arranged within the first drum and thus is driven in the same direction or sense, so that during operation of the system the rolls of the separation device engage in the manner of gears between the rolls of the first drum. The rolls of the separation device are equipped with recesses or depressions connected with a negative pressure source, in order to engage in each case the edge of the lowermost dispositioned flat structure -- here there are processed newspapers. Additionally, the rolls of the separation device are driven about their own axis in a direction opposite to the common direction of rotation of both drums, in order to downwardly pull the engaged newspaper edge between neighboring rolls of the first drum. However, with this action the rolls of the separation device have not yet fulfilled their function. Indeed, they must additionally ensure that the newspapers are slid between the rolls of the smaller drum, and the rolls of the separation device must transport the newspapers during a long and complicated course of movement. As a result, the position of the newspapers is altered a number of times and upon transfer thereof to the conveyor device there do not prevail any clear or fixed conditions. A limited intermediate stack -- as contemplated by the prior art apparatus -- might allow for a certain compensation, but in that case the original stack is not destacked in the sense of single separation of the articles of the stack. Finally, with the aforementioned operations the shape of the newspapers plays a considerable role, and accordingly, whenever the shape changes, something which frequently happens, it is necessary to readjust or convert the apparatus. This constitutes a real disadvantage or burden when considered in respect of the very complicated and costly construction of the separation device.